Fast-moving severe thunderstorm cells dumped heavy rain and hail along the Interstate 83 corridor in Baltimore County before moving along to northwestern Harford County early Friday evening, prompting a tornado warning for about an hour.

The National Weather Service indicated that a radar-indicated tornado moved northeast at 30 mph in the Jarrettsville area of Harford County. The tornado was not immediately confirmed.

A tornado warning first issued in Baltimore County at 6:30 p.m. was extended to 7:30 p.m. and expanded to include northwestern Harford County.

There were no immediate reports of damage.

"We are working closely in contact with folks in Baltimore County, Baltimore City and Harford County if they need any help from us. We have not gotten any damage reports yet," Maryland Emergency Management Agency spokesman Ed McDonough said.

"We want people to take precautions. As you've been telling them, get to an interior room like the basement and stay away from windows. We just want people to be as safe as they can," McDonough added. (continued, next page)

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Harford County fire and emergency officials posted on Facebook that they have received no reports of damage, but fire companies in the northwestern part of the county were responding to calls for wires down and tree fires.

As the storm moved fast to the northeast, hundreds of power customers in Baltimore County lost service.

"It looks like the hardest hit area is Baltimore County with 600 customers that have lost service. We do continue to watch surrounding weather systems that may enter our service area, and we may see those numbers continue to grow," Baltimore Gas and Electric spokeswoman Rachel Lighty said.

If you see a downed wire or have lost electricity, call BGE at 877-778-2222.

Officials advise when a tornado warning is issued:- Head for the lowest level of your building- Interior rooms or doorways are the safest- Stay away from windows- Cover your head and wait for the storm to move past- If caught outside, crouch down in a low-lying area